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When I see generator construction they usually suggest 1 stator and 2 rotors. Answered

Most show 1 set of coils with magnets on a disc on each side.
How would 1 rotor ( with magnets ) and stators ( with coils on ) either side of it compare?

Just to be clear the magnets rotate.


Should work just as well.  It's harder to mount the magnets and get the rotor balanced than if making coils in the rotor.

I've seen several designs that were like this.

One difference will be that you will have a/c instead of choppy d/c.

Thanks for the reply.

But I thought you get a/c from both.

Having the magnets move and the coils stationary is advantageous as mentioned - makes pure sine wave AC - because it has no commutator to get power from internal coils out of the armature.  It is electro-mechanically the soundest design for a pm generator to have the magnets on the rotor.

Coils on either side of bipolar magnets would utilize both sides of the magnetic field.  Magnets on a magnetic surface conduct the magnetic flux from the back side back into the front side to allow for a stronger magnetic field on the working side.  Having 2 magnetic plates and one set of coils is the most flux you can get into a smaller coil area.

From what I have read one of the problems is 'cogging'. I was thinking that with coils on either side of the magnets they could be offset half the width of the magnets so this is reduced. Is this correct?
Also if you had steel behind each set of coils would this improve things, maybe stronger flux lines?

Steel would make for much stronger flux - allowing it to pass through the steel and be 'twice' as strong on the magnet side.  **that's a fudge number, its probably less, but it does help.

*and welcome to instructables!  Congrats on the pro :D